Oxygen-producing candle

ABSTRACT

In an oxygen-producing candle having an ignition core that is ignited by flash powder, improved ignition is obtained by disposing a metal screen between the ignition core and the flash powder.

United States Patent 1111 3,615,251

[72] Inventor Frederick K. Klenk [56] References Cited Forward Township,Butler County, Pa. UNITED STATES PATENTS 1 PP 384,221 2,764,475 9/1956Bovard et al 23/281 1 Flled 11, 1969 3 377 956 4/1968 Van Deene Emerson102/102 [45] Patented Oct. 26, 1971 [73] Assignee Mine Safety AppliancesCompany Examiner-James y n,

Pittsbur h, Pa, At10rneyRonald H. Shakely [54] OXYGEN-PRODUCING CANDLE 4Claims, 2 Drawing Figs.

52 U.S. Cl 23/281, 23/221,165/185,102/102,102/70 [51] Int. Cl BOlj 7/00ABSTRACT: In an oxygen-producing candle having an igni- [50] Field ofSearch 23/281 tion core that is ignited by flash powder, improvedignition is 221; 165/185; 102/102, 103,70,37.8;252/186: obtained bydisposing a metal screen between the ignition 187 core and the flashpowder.

PATENTED 0m 2 6 I97! INVENTOR: H'ederick K. K lenk OXYGEN-PRODUCINGCANDLE This invention relates to candles that generate oxygen as theyare burned, and more particularly to such candles having improvedignition characteristics.

The candles of this invention are suitable for use in oxygenproducingapparatus such as is shown in Bovard and Hamilton, U.S. Pat. No.2,758,015. When an oxygen candle burns in such apparatus, it mustproduce oxygen in a volume great enough to sustain life before thechemical in the apparatus, that reacts with exhaled breath to removecarbon dioxide and produce oxygen, is functioning well enough to do italone. This chemical reaction is retarded at low temperatures, as in theArtic and at high altitudes, so it is necessary that the oxygen candleperform reliably at low temperatures. Government procurement regulationsrequire testing of the apparatus at 30 C. as a satisfactory measure oflow-temperature performance.

In the ignition train to ignite the candle, a powder primer is fired toignite a flash powder; the flash powder ignites in turn an ignition corematerial that burns rapidly, and in turn ignites the main candle body toproduce oxygen. In the manufacture of such candles, even with theexercise of tight specifications and strict quality control practices,lots are frequently rejected because of total or partial ignitionfailure particularly at low temperatures.

This invention is based on my discovery that such ignition failuresresult from a failure of the flash powder to properly ignite theignition core of the oxygen candle and that such failures can besubstantially eliminated by disposing a metal screen between the flashpowder and ignition core.

The invention is illustrated in the accompanying drawings in which FIG.1 is a plan view of the candle partly broken away to show the screen andoxygen producing material, and

FIG. 2 is a vertical section taken on line 11-11 of FIG. 1.

Referring to FIGS. 1 and 2, a cup 1, which is preferably cylindrical, isseated in the base 2 of a canister such as shown in U. S. Pat. No.2,758,015. The bottom of the cup is provided in its center with anopening registering with a similar opening in the base of the canister.A flanged sleeve 3 extends up through these openings and has a threadedupper end on which a nut 4 is screwed to clamp the cup and canister basetightly together. A primer 6 is mounted in the lower end of the sleeve,while a charge 7 of flash powder is pressed into the upper end of thesleeve. A body 8 of oxygen-producing material, of well-known compositionthat gives off oxygen while it is burning, has a recess 9 in its bottomso it can fit over nut 4, and a central cavity opening into the recess 9leaving a peripheral shoulder 10. The cavity is filled with an ignitioncore 11. A metal screen 12 is situated in the recess between theignition core and preferably abutting the nut 4 and the annular shoulder10 formed by the end wall of the recess as well as the ignition core.The flash powder does not extend to the end of nut 4 so that, in thepreferred embodiment, the flash powder is spaced from the screen. Thescreen may be made of any metal or alloy that will withstand the heatgenerated by the flash powder, suitably metals or alloys resistant tooxidation such as brass or stainless steel. Standard 10 to 50 meshscreens are suitable although larger or smaller mesh screens may be usedif desired.

Inside the upper part of the cup there are means for filtering out smokethat may be produced by the burning candle. This may consist of adimpled metal plate supported on top of the candle body, a screen 13 ontop of the plate, a layer or two of filtering material 14, anotherscreen 15, and a ring 16 pressed down onto the latter by indentations 17in the top of the cup around it.

The chlorate candle 8 may be a cast body or a compact of powdered orgranular materials according to conventional practice. Chlorate candlescontain predominantly an alkali metal chlorate or perchlorate, usuallysodium chlorate; a metal, usually iron, although other reactive metalsmay be used; and generally minor amounts of a binder such as fiberglasand other ingredients such as barium peroxide. Representative suitablechlorate candle compositions are disclosed in U.S. Pat. Nos. 2,469,414,3,089,855, 3,l74,936, 3,207,695 and 3,293,187.

The ignition core 11 is a conventional, easily ignited pyrotechnic thatburns rapidly without flashing, suitably a compacted mixture of metalpowder and an inorganic oxidizer with or without diluents, binders orother minor components. The ignition core may contain the same materialas the candle body, but with a higher amount of metal to give a fasterburning rate. Ignition cores may be staged, that is, having portions ofdifferent compositions having different burning characteristics. Forexample, suitable ignition cores may be a compact of from about 20 to 40percent iron powder, from about 15 to 40 percent sodium chlorate, fromabout 10 to 20 percent barium peroxide, and from about 5 to 20 percentfiberglas. A variety of ignition core materials are well known and havebeen used for reliably igniting chlorate candles.

The ignition core is ignited by flash powder 7, that may be any of thewell known easily ignitable first-fire pyrotechnic mixtures that, whenignited, burn rapidly to produce a sudden temporary luminous flame. Itis preferred to use a mixture of a finely divided metal, such asaluminum, magnesium, titanium, iron or nickel and an inorganic oxidizingagent, for example, alkali metal or alkaline earth metal nitrates,chlorates and perchlorates.

The combustion characteristics of such flash powder mix tures may varyconsiderably from batch to batch of the same composition because ofvariations in the materials used that are difficult to detect, define ordetermine, such as minor variations in size and shape of the particles,particle surface area and condition, and small amounts of impurities.Accordingly, it has been found necessary to run extensive lowtemperature performance tests on completely assembled oxygen candles toassure that individual batches of flash powder will provide reliableignition performance.

I have found that reliable candle ignition is obtained over widevariations in flash powder characteristics when a metal screen ispositioned between the flash powder and the ignition core. Thus, oxygencandle ignition trains, designed according to conventional practice forparticular configurations and compositions, can be made to accommodatewide manufacturing tolerances in flash powder without a high rejectionrate of candles.

To illustrate the effectiveness of this invention, a high unpredictablerejection rate for a particular lot of flash powder was experienced whenusing oxygen candles without screen 12, but otherwise as shown in FIGS.1 and 2. Flash powder 7 was from a single lot of a mixture of 30 percentnickel, 20 percent titanium, 45 percent potassium perchlorate and 5percent infusioral earth. The ignition core composition was 30 percentiron, 30 percent sodium chlorate, 25 percent fiberglas and 15 percentbarium peroxide. In firing tests made at -30 C., four candles failedcompletely to ignite and I4 candles generated less than one-half literof oxygen in the first 15 seconds after ignition, a substandard amount.In the entire 80 tests, the amount of oxygen generated in the first l5seconds after firing ranged from 0 to 1.1 liters with an average of 0.67liters.

In 73 tests of the candles of FIGS. 1 and 2, including a 14- mesh screenof 0.02-inch-diameter brass wire and using all materials identical tothose in the previously described tests, there were no ignition failuresat 30 C. and the oxygen generated in the first 15 seconds after firingranged from 0.9 to 1.4 liters with an average of l.ll liters.

Although the exact mechanism by which this invention provides improvedignition is not known, it is believed the screen serves to disperse theeffective area of the flame from the flash powder, prevents ignitioncore material from disengaging from the candle body, the core may shrinkor become partially molten, and acts as a heat sink. It will berecognized that this invention will be advantageous in any oxygen candleignition train in which an ignition core is ignited by a flash powder.

I claim:

IOIOO? 0064 1. An oxygen candle comprising a body of material thatproduces oxygen on burning and a core of ignition material having anignitable face, a recess in said candle having an end wall comprisingsaid ignitable face, a metal screen covering and abutting said end wall,cover means closing said recess to form a chamber and supporting a bodyof flash powder within the chamber spaced from said screen, and means toignite the flash powder from outside said chamber.

2. An oxygen-producing candle according to claim 1 in 0 which said endwall comprises an annular surface of said oxygen producing material.

3. An oxygen-producing candle according to claim 1 in which said covermeans engages said screen.

4. An oxygen candle according to claim 3 in which said cover meanscomprises an inwardly extending tubular conduit engaging said screen,said conduit being partially filled with flash powder.

2. An oxygen-producing candle according to claim 1 in which said endwall comprises an annular surface of said oxygen producing material. 3.An oxygen-producing candle according to claim 1 in which said covermeans engages said screen.
 4. An oxygen candle according to claim 3 inwhich said cover means comprises an inwardly extending tubular conduitengaging said screen, said conduit being partially filled with flashpowder.